1. Field of the Invention
The present invention relates generally to the construction of reinforced concrete beams and more specifically it relates to a method for fabricating a reinforced wide shallow concrete beam with increased shear resistance efficiency which greatly increases the effectiveness of stirrups in contributing to shear resistance.
2. Description of the Related Art
Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field.
Reinforced concrete beams have been in use for years in building constructions. Wide beams in concrete buildings are generally constructed to be hidden by designing the wide beams to have the same depth as the supported floor (i.e. in a joist construction). Such wide shallow beams are generally supported on elongated columns in constructions of residential buildings.
In the past, shear strength in reinforced concrete beams, or Vn, has been calculated as the summation of contributions of concrete and stirrups as shown in the below equation:Vn=Vc+VsL.
The first parameter, Vc, is the concrete contribution to shear strength and is generally expressed by empirical equations involving a number of influencing parameters. For wide beams, support width has also been considered as an additional parameter which causes geometric differences and induces disturbed force flow.
The second parameter, VsL, is the stirrup contribution to shear strength and has previously been formulated for vertical stirrups as:
            V      sL        =                            A          v                ⁢                  f          yv                ⁢        d                    s        L              ,where, sL is the longitudinal spacing of stirrups, Av is the vertical legs area, d is the effective depth and fyv is the yield strength of stirrups. However, this equation does not include a direct parameter for the transverse spacing of stirrup legs. Building codes in various countries appear to differ in their treatment of the transverse spacing issue. For example, Eurocode 2 suggests spacing limits of 0.75 d or 600 mm in both the width and longitudinal direction. In contrast, ACI318-08, which was released by the American Concrete Institute, suggests spacing limits of 0.5 d in the longitudinal direction, but does not provide a limit on the leg spacing in the transverse direction.
While there have been numerous studies conducted on the issue, a consensus has yet to be reached regarding the issue of transverse spacing requirements with respect to wide shallow beams. Because of the inherent problems with the related art, there is a need for a new and improved method for fabricating a reinforced wide shallow concrete beam which utilizes new guidelines for computing stirrup contribution to shear strength to ensure adequate safety of wide shallow members for one-way shear.